A 360-degree panoramic camera typically includes a plurality of conventional lenses or a plurality of wide-angle camera lenses, which are used by the camera to perform synchronous acquisition of a 360-degree scene and generate a complete spherical projection image. Using a panoramic camera including two fisheye camera lenses can reduce the complexity of stitching algorithms and achieve rapid stitching. However, fisheye lenses may produce image distortions. It is therefore necessary to calibrate the fisheye lens when a fisheye lens is manufactured.
With currently available technology, intrinsic and extrinsic parameters of a fisheye lens are calibrated separately. When the intrinsic parameters are being calibrated, a calibration board covers the vast majority of the area on the image captured by the lenses, particularly at the edges. Therefore, a plurality of images must be acquired, and it is necessary to move the camera or calibration board. After images are obtained, the projection error between the image coordinates of recognition feature points on the image and the corresponding coordinates on a chessboard plane is calculated, and the error is set as an optimization target to perform iteration and optimize all the intrinsic and extrinsic parameters of the lenses. When the extrinsic parameters are being calibrated, calibration boards need to be set up in overlapping regions of the images captured by the lenses. Next, the extrinsic parameters of each lens in relation to the calibration board are respectively calculated, after which the extrinsic parameters between the lenses are calculated.
However, when intrinsic parameters are calibrated, the larger the coverage of a calibration board on an image, the better the calibration results. Therefore, the camera or calibration board needs to be moved as much as possible, resulting in cumbersome and time-consuming operations and low productivity. When extrinsic parameters are calibrated, the calibration board must be simultaneously covered by images captured by two lenses, which generally results in the calibration board having a smaller coverage area on the images, thereby introducing a relatively large error. Moreover, the intrinsic parameters and extrinsic parameters of a lens are calculated separately, and a valid assessment cannot be provided for the distortion curve of the intrinsic parameters along the edge of the angle of view (FOV), frequently resulting in suboptimal results for extrinsic parameter calibration and poor final stitching effect as well.